Iran may have been involved in an attack that resulted in hackers acquiring bogus digital certificates for some of the Web's biggest sites, including Google and Gmail, Microsoft, Skype and Yahoo, a certificate issuing firm said today.

The bogus certificates -- which are used to prove that a site is legitimate -- were acquired by attackers last week when they used a valid username and password to access an affiliate of Comodo, which issues SSL certificates through its UserTrust arm.

Today, Comodo's CEO said his company believes the attack was state-sponsored and pointed a finger at Iran.

"We believe these are politically motivated, state driven/funded attacks," said Melih Abdulhayoglu, the CEO and founder of Comodo, a Jersey City, N.J.-based security company that is also allowed to issue site certificates.

"One of the origins of the attack that we experienced is from Iran," Abdulhayoglu said in an online statement. "What is being obtained would enable the perpetrator to intercept Web-based email/communication and the only way this could be done is if the perpetrator had access to the country's DNS infrastructure (and we believe it might be the case here)."

Comodo's security blog offered more details of the Iranian connection and claimed that at least two Iranian IP addresses and one ISP were involved.

"The IP address of the initial attack ... has been determined to be assigned to an ISP in Iran," said Comodo. "A Web survey revealed one of the certificates [was] deployed on another IP address assigned to an Iranian ISP."

That server went offline shortly after Comodo revoked the certificates.

Fake certificates can be used by attackers to fool users into thinking that they're at a legitimate site when in reality they're not, said Andrew Storms, director of security operations at nCircle Security.

"They would be used in a 'man in the middle' kind of attack," said Storms. "They could use [the bogus certificates] to host a site that looks like one of these real sites, then capture people's log-ins."

Comodo echoed Storms' take on the attack's implication but speculated that it was a government-backed effort.

"It does not escape [our] notice that the domains targeted would be of greatest use to a government attempting surveillance of Internet use by dissident groups," Comodo said. "The attack comes at a time when many countries in North Africa and the [Persian] Gulf region are facing popular protests."

According to a Microsoft security advisory published earlier today, the nine fake certificates were issued for login.live.com, mail.google.com, www.google.com, login.yahoo.com, login.skype.com, addons.mozilla.org and Global Trustee.

Three certificates were acquired for Yahoo, said Microsoft, and one each for the others.

The attack and acquisition of the certificates has prompted Google, Microsoft and Mozilla to issue updates so users of their browsers will be warned if they try to reach a site that's serving up one of the phony certificates.

On Tuesday, Mozilla shipped updates for its Firefox 3.5 and Firefox 3.6 browsers to do the same; it had already revamped Firefox 4 before the new browser's Tuesday launch.

Microsoft followed today with an update to all Windows users that adds the nine certificates to the operating system's blacklist, which Internet Explorer accesses. The update has been pushed to Microsoft's Windows Update service for users running Windows XP, Server 2003, Vista, Server 2008, Windows 7 and Server 2008 R2.

Comodo said the attackers obtained the certificates on March 15 using a username and password assigned to a company partner in southern Europe. It has not identified the partner but admitted it didn't know all the details.

"We are not yet clear about the nature or the details of the breach suffered by that partner, other than knowing that other online accounts -- [although] not with Comodo -- held by that partner were also compromised at about the same time," Comodo said.

Storms called Comodo's failure a major security event. "It's a big deal when a trusted authority issues something it clearly shouldn't have," Storms said. "People start second-guessing whether a site is really what it says it is."

It could also be a financial hit to Comodo, Storms added, pointing out that certificate-issuing authorities regularly post bonds for liability reasons or to prepare for potential lawsuits when problems crop up.

"Comodo has put money on the validity of their certificates," Storms said.

It isn't surprising that attackers would be very interested in acquiring certificates to such major Web players as Google, Microsoft and Yahoo.

"They're getting a lot for their buck," said Storms, referring to the hackers' efforts.

Comodo said it reacted to last week's attack "within hours" and revoked the certificates. "At no time were any Comodo root keys, intermediate [certificate authorities] or secure hardware compromised," the company asserted.

Even though the certificates have been revoked, Chrome and Firefox users should be sure to update their browsers, said Storms, and IE users should deploy today's Windows update from Microsoft.